So you mean, we can build templates/themes pages which we can export and use them with Remix and Gatsby CMS?

Hi Virally,
no, I mean that a React Bricks project really is a Gatsby, Remix or Next.js project, using the React Bricks library.
Gatsby, Remix and Next.js are React Framework to create websites, either using Static site generation (like Gatsby and Next.js) or Server-side rendering (like Remix and Next.js which can do both).
So, if you use SSG with Gatsby or Next.js you are generating a static site, but the generation process calls the React Bricks APIs to generate all the pages. So you need React Bricks to edit the content and generate the static site. Anyway, this has nothing to do with limits: you have limits on React Bricks CMS APIs. If you have 300 pages, you can just create 300 pages.
I suggest you to purchase the deal, start the CLI (npx create-reactbricks-app) and see how it works: you have 30 days to request a refund if it's not what you need.
In this way you will see that when you scaffold a project with the CLI you will choose the React framework and you will have a complete project set up for you, ready with static site generation.

Do you only host the APIs and thats it? I thought I read in another question that you host images and videos also. And if you do host the images, videos etc, and we're already using a headless CMS, then what would get stored on netlify?

I'm referring to static site by the way.

We host the content through our APIs and also the assets that are uploaded using our <Image> and <File> components.
Why do you need another headless CMS, instead of just using React Bricks?

Thank you,
Matteo